Antagonistic effects of the SRp30c protein and cryptic 5′ splice sites on the alternative splicing of the apoptotic regulator Bcl-x
Antagonistic effects of the SRp30c protein and cryptic 5′ splice sites on the alternative splicing of the apoptotic regulator Bcl-x
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DOI：
10.1074/jbc.m800353200
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发表时间：
2008-08-01
影响因子：
4.8
通讯作者：
Chabot, Benoit
中科院分区：
文献类型：
--
作者：
Cloutier, Philippe;Toutant, Johanne;Chabot, Benoit
选择性5‘端剪接位点的选择允许Bclx产生两种不同的异构体，对细胞凋亡有相反的作用。促细胞凋亡的Bclx(S)变异体通过特定的顺式作用外显子元件上调神经酰胺和下调蛋白激酶C的表达，其中一个外显子元件与SAP155结合。异质性核核糖核蛋白(HnRNP)F/H蛋白和Sam68与hnRNP A1协同作用也促进了对Bcl-Xs5‘剪接位点的剪接。在这里，我们已经确定了影响剪接到抗细胞凋亡的Bclx(L)亚型5‘剪接点的外显子元件。在位于Bclx(L)供体位点上游的86个核苷酸区域(B3)中，我们鉴定了两个刺激Bclx(L)5‘剪接位点剪接的元件(ML2和AM2)。SRp30c与这些元件结合，并在体内外以ML2/AM2依赖的方式将剪接转移到Bclxl的5‘剪接点。B3区还包含一个抑制Bclx使用的元件(L)。该元件由U1小核糖核蛋白结合，含有两个5‘剪接位点，可在Bclx(L)5’剪接位点突变或ML2/AM2元件缺失时使用。相反，突变隐蔽的5‘剪接位点会刺激对Bclx(L)位点的剪接。因此，SRp30c刺激剪接到Bclx(L)下游的5‘剪接位点，从而减弱上游U1SnRNP结合位点的抑制作用。
Alternative 5' splice site selection allows Bcl-x to produce two isoforms with opposite effects on apoptosis. The pro-apoptotic Bcl-x(S) variant is up-regulated by ceramide and down-regulated by protein kinase C through specific cis-acting exonic elements, one of which is bound by SAP155. Splicing to the Bcl-xS 5' splice site is also enforced by heterogeneous nuclear ribonucleoprotein (hnRNP) F/H proteins and by Sam68 in cooperation with hnRNP A1. Here, we have characterized exon elements that influence splicing to the 5' splice site of the anti-apoptotic Bcl-x(L) isoform. Within a 86-nucleotide region (B3) located immediately upstream of the Bcl-x(L) donor site we have identified two elements (ML2 and AM2) that stimulate splicing to the Bcl-x(L) 5' splice site. SRp30c binds to these elements and can shift splicing to the 5' splice site of Bcl-xL in an ML2/AM2-dependent manner in vitro and in vivo. The B3 region also contains an element that represses the use of Bcl-x(L). This element is bound by U1 small nuclear ribonucleoprotein and contains two 5' splice sites that can be used when the Bcl-x(L) 5' splice site is mutated or the ML2/AM2 elements are deleted. Conversely, mutating the cryptic 5' splice sites stimulates splicing to the Bcl-x(L) site. Thus, SRp30c stimulates splicing to the downstream 5' splice site of Bcl-x(L), thereby attenuating the repressive effect of upstream U1 snRNP binding sites.